Physical and photo-electrochemical properties of CuO thin film grown on µc-Si:H/glass. Application to solar energy conversion

Abstract

The Physical and photo-electrochemical properties of CuO grown on microcrystalline silicon thin films (µc-Si:H) by heating copper film were investigated. The Raman spectrum for µc-Si: H exhibits a peak at 520 cm−1 confirming its good crystallinity with a crystalline volume fraction of 91%. The X-ray diffraction pattern shows narrow peaks with a monoclinic symmetry. The indirect optical transition (1.19 eV) is well matched to the solar spectrum and the low transmittance (<7%at 400 nm), indicating a good optical quality. The capacitance measurements, performed in Na2SO4 electrolyte indicate that CuO/µ-Si:H electrode acts as n-type semiconductor with a donor density ND of 4.88 × 1019 cm−3 implying the existence of oxygen vacancies in the film. The potential of its conduction band (−0.563 VSCE) made up of Cu-eg orbital, is more cathodic than the O2/O2 level (−0.3 VSCE), but not enough to yield O2 reduction under solar light. By contrast, the electrons in the Cu2+: 4 s level excited by the UVA of the solar radiation, leading to oxidation of 26% of RhB (10 ppm) mainly by the O2 radicals within 60 min.